The present invention relates to a wafer transport apparatus that can transfer multiple semiconductor wafers (wafers in the following) between wafer holding racks with multiple positions all at once, and in particular, it relates to a wafer transport apparatus suitable for a cassette unit provided for a batch processing ion implantation equipment.
In a batch processing ion implantation equipment, ion implantation is carried out simultaneously on multiple wafers in a vacuum chamber. Thus, a cassette unit is set up to introduce and remove the multiple wafers from the air and vacuum. This cassette unit is outside of the vacuum chamber, which is the processing chamber, when ion implantation processes are being carried out. When ion implantation processing is completed, the cassette unit is set in the vacuum chamber, and along with receiving processed wafers, it takes away unprocessed wafers. After taking them away, the cassette unit is removed from the vacuum chamber, and ion implantation processing recommences. The cassette unit, which has been removed from the vacuum chamber, has processed wafers unloaded one at a time by a handling unit and transferred to an unloading cassette, and along with this, unprocessed wafers are transferred one at a time from a loading cassette.
If the ion implantation processing has been completed at this time, the cassette unit is again set in the vacuum chamber, and the above operations are repeated.
As can be seen from the above explanation, in the ion implantation equipment up to this point, transfers between the cassette unit and the unloading cassette and the cassette unit and the loading cassette are carried out one wafer at a time. Therefore, a great deal of time is necessary for transferring all of the wafers from one cassette. This means that when the ion implantation processing time is short, the capacity for processing wafers per unit time is low.